var timeout	= 100;
var timer	= 0;
var item	= 0;

// open hidden layer
function showmenu(id)
{	
	//keep menu open
	keepopen();

	// close old layer
	hidemenu();

	// get new layer and show it
	item = document.getElementById(id);
	item.style.visibility = 'visible';

}
// close showed layer
function hidemenu()
{
	//hide old layer
	if(item) item.style.visibility = 'hidden';
}

//user has moved off menu; prepare to close
//user may be moving to submenu
function prepclose()
{
	//begin counting down to close menu
	timer = window.setTimeout(hidemenu, timeout);
}

// cancel close timer
function keepopen()
{
	//stop the countdown, reset the timer
	//user has moved to a submenu
	if(timer)
	{
		window.clearTimeout(timer);
		timer = null;
	}
}